Dash will automatically connect with your vehicle to track your driving.
Once you've configured Dash the first time, it will try to connect whenever you're in the car. Just make sure your OBD-II is plugged in, and have Dash running in the background on your phone.*
Dash does not need to be the active app on your phone for auto-connect to work, so go ahead and use Waze or Pandora simultaneously while you drive.
*iOS will sometimes auto-kill apps in the background, interfering with Dash auto-connect. If that happens, just open the app and click connect to log your trip.